High-voltage electric rotary machine and a method for cooling the conductors of said machine

ABSTRACT

The aim of the invention is to ensure efficient coolilng in an electric rotary machine ( 2 ), in particular in a high-voltage generator. To achieve this, the invention provides a coolant channel ( 10 ) which extends in a radial direction and in which a number of high-voltage conductors ( 14 ) are located. A coolant gas is preferably used as the coolant. The advantage of positioning the high-voltage cables ( 14 ) in the coolant channels ( 10 ) is that the coolant comes into direct contact with said high-voltage cables ( 14 ), thus ensuring efficient and uniform cooling.

[0001] The invention concerns an electric rotary machine, in particulara generator, with a stator and with a stator coil, which has a number ofhigh-voltage cables. The invention also concerns a procedure for thecooling of such electric rotary machines.

[0002] Conventional electric rotary machines, for example,turbo-generators, are designed for a relatively low voltage of 10 . . .25 kV. However, the rotary machine to which this invention refers isdesigned for high voltage. In this case, high voltage is understood tobe the range from 30 kV to several 100 kV. Such a high-voltage generatoris specially designed for the power supply of long-distance networks,for example, for 110 kV. The main advantage of the high-voltagegenerator is that it can feed power directly into the long-distancenetwork, without needing a transformer.

[0003] An important difference between a conventional generator and thehigh-voltage generator consists in the design of its coil, inparticular, its stator coil. In particular, this concerns the individualcables, which, in the case of high-voltage generators, are designed ashigh-voltage cables. Based on the clearly higher voltages, thesehigh-voltage cables must have a fundamentally different insulation thanthe cables of conventional generators. The high-voltage cables aresimilar to conventional high-voltage cables and, as a rule, have abundle of cable lanes, which are covered by an appropriate insulation,specifically plastic insulation.

[0004] Based on the distinctly higher voltages, high-voltage generatorsdemand a different construction with regard to electric/magneticboundary conditions as well as with regard to the required cooling.

[0005] A cooling system for such a high-voltage generator is known fromWO 97/45914. The stator of this generator is layered by individualsegment-forming sheets of metal in the longitudinal direction such thatextending grooves are formed in the radial direction. Severalhigh-voltage cables, which are arranged next to each other in the radialdirection, run in each of the grooves. The groove has a complexgeometry; i.e., its sidewalls are formed by a stringing together ofcurvatures corresponding to the individual high-voltage cables. Coolingchannels that extend in the axial direction are provided between everytwo such grooves. The actual cooling cable, with a coolant flowingthrough it, is fed through the corresponding cooling channel. Thisarrangement requires an embedded material for the cooling cable, inorder to achieve a good thermal contact between the cooling cable andthe corresponding tooth-like stator segment.

[0006] The invention is based on the function of guaranteeing anefficient cooling for a high-voltage generator.

[0007] In accordance with the invention, this function is fulfilled byan electric rotary machine, in particular by a generator, with a statorand a stator coil, which has a number of high-voltage cables, whereby acoolant channel is provided, in which a number of the high-voltagecables are arranged.

[0008] An immediate cooling of the individual high-voltage cables isenabled by the arrangement of the high-voltage cables in the coolantchannel. The heat is diverted directly by a coolant flowing through thecoolant channel. Thus, there are no other components arranged betweenthe coolant and the high-voltage cables that impair the thermalconductibility and thereby the cooling capacity.

[0009] The arrangement of the high-voltage cables in the coolant channelis thus comparable to the known state-of-the-art arrangement in a grooveof the stator, with the important difference that, with the knowngenerator, the high-voltage cables are cooled only indirectly. Thegroove is brought in as the coolant channel. The high-voltage cablesthereby extend preferably in the axial or longitudinal direction of thegenerator and are arranged next to each other in the radial direction inthe coolant channel.

[0010] For a simple construction of the stator, this is preferablyseparated into stator segments that form a circular ring as seen fromthe cross-section, whereby each stator segment has at least one coolantchannel, in which several high-voltage cables are arranged. Through thearrangement of the coolant channels in each individual segment, anefficient and even cooling is realized.

[0011] The coolant channel is preferably designed as a cool gas channel;i.e., the cooling takes place, for example, via air or, in particular,with turbo-generators also via hydrogen. Compared to an oil-cooledgenerator, such a gas-cooled generator has advantages with respect tothe coolant circulation method.

[0012] In order to achieve a particularly simple constructivearrangement, a preferred design form of the coolant channel has arectangular cross-sectional geometry.

[0013] In order to effectively use the room available within the stator,the coolant channel extends outward preferably in the radial direction.

[0014] In terms of a simple design, this take place in stages.

[0015] This advantageously enables, with the increasing width of thecoolant channel, an increase in the number of high-voltage cablesarranged next to each other vertically in the radial direction.

[0016] In accordance with the invention, this function is also fulfilledby a procedure for cooling an electric rotary machine, in particular,for cooling a generator, whereby the rotary machine has a stator with astator winding, which comprises a number of high-voltage cables, andwhereby the high-voltage cables are cooled immediately by a coolant.

[0017] This procedure advantageously uses the channel, in which thehigh-voltage cables run, as the guide for a coolant. An immediate,efficient, and even generator cooling is thus guaranteed.

[0018] The advantages mentioned with respect to the rotary machine andpreferred design forms should be transferred to the procedure in ananalogous fashion. Further advantageous arrangements of the procedureare to be taken from the sub-claims.

[0019] Design examples of the invention will be described in more detailbelow using the drawing. Each of the following is shown in verysimplified figures:

[0020]FIG. 1 a sector from a cross-section through a generator,

[0021]FIG. 2 a coolant channel with a rectangular cross-section and withinternal high-voltage cables and

[0022]FIG. 3 a coolant channel with a gradually expanding cross-section.

[0023] In accordance with the cut-out, segment-like representation of across-section through a generator 2 designed as a high-voltage generatorbased on FIG. 1, a generator 2 has a stator 4, which surrounds a rotor 8in circular-ring form upon the formation of an air opening 6. The stator4 has a number of grooves that are designed as coolant channels 10.These run in the longitudinal direction of generator 2; i.e., they runvertically to the paper level and each extend out in the radialdirection.

[0024] Each of the coolant channels 10 is arranged within a statorsegment 12. The individual stator segments 12 have an essentiallytrapeze-like cross-sectional surface. The individual stator segments 12form the ring-shaped stator 4.

[0025] A number of high-voltage cables 14 are arranged within each ofthe coolant channels 10. These run in the longitudinal direction ofgenerator 2 through stator 4 and are arranged next to each other in theradial direction within the coolant channels 10. The high-voltagechannels 14 thus form a row within a coolant channel 10 and releasegusset-shaped cross-sections.

[0026] The coolant channels 10 and the rows of high-voltage cables 14extend out beginning from the rotor-side interior 16 in the radialdirection. The high-voltage cables 14 form the non-represented coil ofstator 4.

[0027] For cooling of the high-voltage cables 14, a coolant, inparticular a cool gas, is fed through each of the coolant channels 10.The coolant is thus in immediate contact with the outer surface of thehigh-voltage cables 14 and causes an efficient and, above all, uniformcooling of the individual cables. As additional cooling, further coolingcables known from the state-of-the-art can be used to cool the stator 4.These are, for example, arranged between the individual coolant channels10 as well as in the radial direction on the coolant channels.

[0028] As opposed to the known structure of a high-voltage generator,where high-voltage cables 14 are arranged in grooves open to air opening6, the individual coolant channels 10, based on the design in FIG. 1,are locked on the interior side 16 in order to enable targeted coolantguiding. Coolant channels 10, in particular, are locked tightly byblocks 17, as can be seen in FIG. 2 and FIG. 3.

[0029] The complex state-of-the-art geometry with the arched sidewallsis also taken into consideration for coolant channels 10. However, thedesign with the rectangular cross-section surface in accordance withFIG. 1 advantageously allows easier production as well as a comparablyeasy calculation of the appearing magnetic and/or electric fields.

[0030] The advantages of the arrangement of the high-voltage cables 14in coolant channels 10 or the advantages of the design of the knowngrooves as coolant channels 10 are as follows: additional cooling cablescan be foregone due to the efficient cooling. In particular, gas coolingis sufficient and, thus, a liquid coolant, like water or oil, is notnecessary. Secure and easy cooling is also guaranteed through the directcontact of the coolant on the cable surface. Additionally, the freespace between the individual high-voltage cables 14 is used efficiently.The design of coolant cables 10 as rectangular channels advantageouslyprovides a comparably large streaming cross-section, so that a high coolgas rate is attainable.

[0031] In accordance with the enlarged figure of an individual coolantchannel 10 as in FIG. 2, width B of the coolant channel is adjusted todiameter D of the individual high-voltage cables 14. The high-voltagecables 14 have an interior core 16, which is preferably formed from abundle of individual cable lanes. Core 16 is surrounded by insulation18, which is preferably a common plastic insulation for high-voltagecables. The individual high-voltage cables 14 lie directly next to eachwithin coolant channel 10. Between them and coolant channel 10,individual hollow spaces 20 are formed, through which the coolant flowsvertically to the paper level.

[0032] In accordance with FIG. 3, coolant channel 10 is formed graduallyand extends outward starting from its inner rotor side 16 in the radialdirection upon the formation of a step 22. Width B1 of coolant channel10 below step 22 is fitted to diameter D of high-voltage cable 14 andwidth B2 above step 22 is fitted to doubled diameter D so that twohigh-voltage cables 14 can be arranged next to each other in coolantchannel 10. This design, which extends in the radial direction, ofcoolant channel 10 guarantees the efficient use of space in stator 4.Instead of the step-like design of the consistent diameter D ofhigh-voltage cable 14, an alternative space usage design can also berealized in that coolant channel 10 constantly opens and in that, inparticular, diameter D of the individual high-voltage cables 14increases at the same time.

[0033] Within the groove developed as coolant channel 10, thehigh-voltage cables are determined preferably with non-representedholding elements, e.g., with clamps and with tongue elements, in orderto prevent the relative movement of high-voltage cables 14 with respectto each other and with respect to the stator body as a result of forcesaffecting them or as a result of vibrations.

1. Electric rotary machine (2), in particular, a generator, with astator (4) and with a stator coil, which has a number of high-voltagecable (14), characterized in that a coolant channel (10) is provided, inwhich several of the high-voltage cables (14) are arranged:
 2. Machine(2) as per claim 1 characterized in that the stator (4)—seen in across-section diagram—is separated into stator segments forming acircular ring and in that each of the stator segments (12) has a coolantchannel (10), in which several of the high-voltage cables (14) arearranged.
 3. Machine (2) as per claim 1 or 2 characterized in that thecoolant channel (10) is designed as a cool gas channel.
 4. Machine (2)as per one of the aforementioned claims characterized in that thecoolant channel (10) has a rectangular geometry.
 5. Machine (2) as perone of the aforementioned claims characterized in that the coolantchannel (10) expands especially gradually outward in the radialdirection.
 6. Machine (2) as per claim 5 characterized in that thenumber of high-voltage cables (14), therein arranged next to each othervertically in the radial direction, increases with the increasing width(B) of the coolant channel (10).
 7. Procedure for cooling an electricrotary machine (2), in particular, a generator, which has a stator (4)with a stator coil, which comprises a number of high-voltage cables(14), characterized in that the high-voltage cables (14) are cooleddirectly by a coolant.
 8. Procedure based on claim 7 characterized inthat a cool gas is employed as coolant.
 9. Procedure based on claim 7 or8 characterized in that the coolant flows through a cool gas channelextending in the radial direction, in which several of the high-voltagecables (14) are arranged next to each other in the radial direction.